# Systemd services for docker.

{ config, lib, pkgs, ... }:

with lib;

let

  cfg = config.virtualisation.docker;
  proxy_env = config.networking.proxy.envVars;

in

{
  ###### interface

  options.virtualisation.docker = {
    enable =
      mkOption {
        type = types.bool;
        default = false;
        description =
          ''
            This option enables docker, a daemon that manages
            linux containers. Users in the "docker" group can interact with
            the daemon (e.g. to start or stop containers) using the
            <command>docker</command> command line tool.
          '';
      };

    listenOptions =
      mkOption {
        type = types.listOf types.str;
        default = ["/var/run/docker.sock"];
        description =
          ''
            A list of unix and tcp docker should listen to. The format follows
            ListenStream as described in systemd.socket(5).
          '';
      };

    enableOnBoot =
      mkOption {
        type = types.bool;
        default = true;
        description =
          ''
            When enabled dockerd is started on boot. This is required for
            container, which are created with the
            <literal>--restart=always</literal> flag, to work. If this option is
            disabled, docker might be started on demand by socket activation.
          '';
      };

    liveRestore =
      mkOption {
        type = types.bool;
        default = true;
        description =
          ''
            Allow dockerd to be restarted without affecting running container.
            This option is incompatible with docker swarm.
          '';
      };

    storageDriver =
      mkOption {
        type = types.nullOr (types.enum ["aufs" "btrfs" "devicemapper" "overlay" "overlay2" "zfs"]);
        default = null;
        description =
          ''
            This option determines which Docker storage driver to use. By default
            it let's docker automatically choose preferred storage driver.
          '';
      };

    logDriver =
      mkOption {
        type = types.enum ["none" "json-file" "syslog" "journald" "gelf" "fluentd" "awslogs" "splunk" "etwlogs" "gcplogs"];
        default = "journald";
        description =
          ''
            This option determines which Docker log driver to use.
          '';
      };

    extraOptions =
      mkOption {
        type = types.separatedString " ";
        default = "";
        description =
          ''
            The extra command-line options to pass to
            <command>docker</command> daemon.
          '';
      };

    autoPrune = {
      enable = mkOption {
        type = types.bool;
        default = false;
        description = ''
          Whether to periodically prune Docker resources. If enabled, a
          systemd timer will run <literal>docker system prune -f</literal>
          as specified by the <literal>dates</literal> option.
        '';
      };

      flags = mkOption {
        type = types.listOf types.str;
        default = [];
        example = [ "--all" ];
        description = ''
          Any additional flags passed to <command>docker system prune</command>.
        '';
      };

      dates = mkOption {
        default = "weekly";
        type = types.str;
        description = ''
          Specification (in the format described by
          <citerefentry><refentrytitle>systemd.time</refentrytitle>
          <manvolnum>7</manvolnum></citerefentry>) of the time at
          which the prune will occur.
        '';
      };
    };
  };

  ###### implementation

  config = mkIf cfg.enable (mkMerge [{
      environment.systemPackages = [ pkgs.docker ];
      users.extraGroups.docker.gid = config.ids.gids.docker;
      systemd.packages = [ pkgs.docker ];

      systemd.services.docker = {
        wantedBy = optional cfg.enableOnBoot "multi-user.target";
        environment = proxy_env;
        serviceConfig = {
          ExecStart = [
            ""
            ''
              ${pkgs.docker}/bin/dockerd \
                --group=docker \
                --host=fd:// \
                --log-driver=${cfg.logDriver} \
                ${optionalString (cfg.storageDriver != null) "--storage-driver=${cfg.storageDriver}"} \
                ${optionalString cfg.liveRestore "--live-restore" } \
                ${cfg.extraOptions}
            ''];
          ExecReload=[
            ""
            "${pkgs.procps}/bin/kill -s HUP $MAINPID"
          ];
        };

        path = [ pkgs.kmod ] ++ (optional (cfg.storageDriver == "zfs") pkgs.zfs);
      };

      systemd.sockets.docker = {
        description = "Docker Socket for the API";
        wantedBy = [ "sockets.target" ];
        socketConfig = {
          ListenStream = cfg.listenOptions;
          SocketMode = "0660";
          SocketUser = "root";
          SocketGroup = "docker";
        };
      };


      systemd.services.docker-prune = {
        description = "Prune docker resources";

        restartIfChanged = false;
        unitConfig.X-StopOnRemoval = false;

        serviceConfig.Type = "oneshot";

        script = ''
          ${pkgs.docker}/bin/docker system prune -f ${toString cfg.autoPrune.flags}
        '';

        startAt = optional cfg.autoPrune.enable cfg.autoPrune.dates;
      };
    }
  ]);

  imports = [
    (mkRemovedOptionModule ["virtualisation" "docker" "socketActivation"] "This option was removed in favor of starting docker at boot")
  ];

}